1. Field of Invention
The present invention relates to an image process method, and in particular to an image rectification method.
2. Related Art
The image capturing device such as a digital camera, mobile phone with photoing function, or web cam is widely used in many applications. Users can take pictures or record data by the image capturing device.
For example, in the meeting room, people may write down some ideas or opinions on the whiteboard, or show their slides or pictures on the screen or wall through the projector. Then, the other attendants can note down the information written on the whiteboard or shown on the screen or wall. Now, people have a wiser way to note down the information that is to take photos from the whiteboard, screen or wall. These photos are stored in electronic media such as a memory card, a hard disk or an optical disk, so that they can be easily spread through the above media or e-mail. People can read or study these contents again from the photos after the meeting.
However, some image distortion may occur in these photos because of bad viewing angles, and the rectangle object such as the whiteboard or document looks like a distorted quadrangle. For example, FIG. 1A to FIG. 1C show some distorted objects in the photos. Referring to FIG. 1A, the photo is taken at a small viewing angle, and thus the captured screen region is an arbitrary quadrangle instead of a rectangle. What makes matters worse, referring to FIG. 1B, if the photo is taken at a bad viewing angle, which is far away from the normal line of the rectangle object, parts of the image far away from the image capturing device are too small to be identified. Furthermore, as shown in FIG. 1C, the photo has blurred image and some contents are not clear and can not be recognized.
Therefore, it is an important subject to provide an image rectification method which can rectify the distorted quadrangle in the image.